Duct construction



NOV- 10, 1959 H. A. FREYHOLDT ETAL A2,912,013

DUCT CONSTRUCTION 2 Sheets-Sheet 1 Filed March 23. 1956 VIAWllIlIIIlIIIIlI/A arent Gtlice 2,912,013 Patented Nov. 10,` 1959` DUCTCONSTRUCTION Helmut A. Freyholdt, Santa Monica, and Fred McCown, WestCovina, Calif., assignors to industrial Park Corporation, a corporationof California Application March 23, 1956, Serial No. 573,458

2 Claims. (Cl. 13S-75) This invention pertains to improvements in theconstruction of sheet-metal ducts, such ducts being commonly used inheating and Ventilating systems and wherever it is desired to restrainand convey heating or cooling air, exhaust gas or the like. Theinvention also pertains to locking devices for use in the constructionof sheet metal ducts and the like, said locking devices facilitating theassembly and construction of the ducts Without the necessity ofriveting, bolting or crimping of the metal. The constructions hereindisclosed permit shipment of ducts and duct elements in substantiallyilat form and expedite the assembly of such elements into a completeduct on the job.

The manufacture and installation of ducts presents ntunerous problems.Duets employed for conducting various gases must be made of metal,should be relatively light, gas-tight and easily installed. Ordinarilygalvanized` or tinned sheet metal ranging from 26 to about 30 gauge ispreferred but these heavier sheets are ditcult to form and connect alonglongitudinal edges in making a duct of a desired rectangular crosssection. Rather high quality stock is normally used, the stock being ofvery low Weight or gauge, say 16 or even 18 gauge, in order to permitthe longitudinal edges to be bent and crimped together to make what isknown as a Pittsburgh seam, double seam, grooved seam, standing seam, orother methods of connecting adjacent sections or panels to each y other.Since these various prior types of seams or joints require that themetal be bent very sharply, the protective coating or galvanizing oftencracks or peels, subjecting the duct to attack by constituents of thegases, moisture, etc. or locks have precluded the use of less expensivemetallic sheets and often necessitated the use of alloys, aluminum andother much more expensive materials. In addition, the formation of thoselocks or seams was timeconsuming, and required the use `of special toolsand trained personnel on the job. vSince ducts are relatively light inweight but bulky, the shipment of pre-fabricated ducts was expensive.The present invention relates to improvements and novel methods ofconstruction whereby sheet metal ducts may be manufactured fromrelatively malleable, less expensive sheet metal stock which need nothave the block forming qualities required heretofore. Moreover, theconstruction described hereinafter permits panels from which a duct isto be constructed These prior methods of forming seams Thelockingpstrips frictionally and vpositively grasp and hold marginal edgeareas .and adjacent sheets'- Without necessitating bending, stress orforming of the metal along the edge. Asa' result Ventilating ducts andthe like may be quickly and readily assembled without the use of specialtools.

It is an object of the present invention therefore to disclose andprovide a novel sheet metal duct construction.

A further object of the invention is to disclose and provide lockingdevices capable of being embodied in or used in connection with sheetmetal panels for the construction of ducts or wherever sheet metalpanels need be connected.

A still further object of the invention is to disclose and provide sheetmetal duct constructions whereby relatively light gauge, inexpensive,flat stock may be used, such fiat stock having characteristics ofstrength and rigidity equal to that of much heavier stock. f

These and various other uses, advantages and adaptations of theinvention will become apparent from the following description, referencebeing had to the appended drawings in which certain exemplary forms areillustrated. p

In the drawings:

Fig. 1 is a perspective view of a duct made in accordance with thepresent invention;

Fig. 2 is an enlarged section taken through a corner of the ductillustrated in Fig. 1, the section being taken along the plane II--IlgFig. 3 is an enlarged view of an end portion of a corner locking strip;

Fig. 4 is an end view of a sheet of metal provided with integral lockingdevices along itsY longitudinal edges;

Fig. 5 is an enlarged section of an end locking strip of the characterillustrated in Fig. 1; f-

Fig. 6 is an enlarged view showing the end locking strip before assemblyand tightening; and

Fig. 7 is a section through a part of a reducing frame which may beemployed in reducing the cross sectional area of a duct. l

Although, as previously indicated, the constructions hereinafterdisclosed are capable of being used in the construction of many devicesand pieces of equipment, such as drying ovens, annealing ovens, spraybooths and whateversheet metal construction is indicated, the advantagesof the construction are emphasized in heating and Ventilating ducts ofthe character illustrated in Fig. l'. As there shown the completed ductis formed from upper and lower panels 1 and 2 and side panels 3 and 4connected together at the corners by means of locking devices includingbacking members such as the member to be shipped in a substantially flatform, these substanj F v sheet.

Generally stated, the present invention is directed to a novel lockingstrip capable of being used at corners of a duct or in connecting panelslying in a common plane.

10. Fig. 1 illustrates an end of a duct and it will be noted that acontinuation of the side wall in which panel 4 is positioned'comprisesanother side wall panel 5 which is connected to the end of panel l bymeans of a locking strip 40. Attention is further called to the factthat the longitudinal edges of these side panels 3 and 4 are straightrectilinear edges Without folds or bends and the sarrie comments applyto the top and bottom panels 1 an 2.

The construction of the backing member 10 will be evident from Figs. 2and 3. As there shown the locking means comprises the backing member anda locking strip generally indicated at l2, these two elements beingconnected together by a series of spaced rivets 13.

The backing member 10 may be said to include an anchor portion 14 and alongitudinally extending resist portion on each side thereof andintegral therewith, the resist portions 15 and 16 lying in planesinclined to the plane of the anchor portion 14.

The elongated locking strip 12 is of the same length as the backingmember and is provided with a back portion 17 lying in a planesubstantially parallel to the anchor portion 14, and with longitudinallyextending marginal grasping portions 18 and V1 8' bent toward each otherwith the plane of the back portion 17 and the planes of the graspingportions 18 and 18 assuming the coniiguration of the longitudinal facesof'atrilateral prism so as to present grasping faces 19 and 19',respectively, toward the opposing resist portions and 16, respectively.A longitudinal edge of the top panel 1 is inserted between the resistportion 16 and the grasping portion 18' and is firmly held therebetween.Similarly, a longitudinal edge of the side wall panel 3 is insertedbetween the resist 15 and the grasping portion 18 and is frictionallyand rmly held therein. It may be noted that inasmuch as the graspingportions 18 are bent out of the back 17 a rounded corner is presented tothe incoming edge of a panel to be held and locked by the locking means10, this rounded corner facilitating insertion and guiding the edge of apanel such as the panel 3.

It hasbeen discovered that a locking means of the character Ydescribedholds and positions panels of a duct with remarkable tenacity andmaterially enhances the strength and rigidity of the completed duct.Frictional engagement between the grasping portions and the resistportions is partly due to the prestressed construction employed, thisprestressed construction being made more evident from a contemplation ofFig. 3. Fig. 3 illustrates in perspective an end portion of a lockingmeans before it receives adjacent longitudinal edges 'of panelsconverging at a corner. In Fig. 3 a true 90 angle is indicated by thedash lines 20. It will be noted that the resist portions 15 and 16 ofthe elongated backing member 10 have been formed or bent so as toinclude an angle of slightly less than 90. Similarly, the graspingportions 18 and 18 of the locking strip 12 'have been bent inwardlytoward each other so as to make an included angle of less than 90 butmore than 45 with the back 17 of the locking strip. When the backingmember 10 and the locking strip are connected together by the series ofrivets or the like 13 (such rivets preferably passing through the anchorportion of the backing member and the back of the locking strip) theoutwardly directed grasping faces of the grasping portions 18 and 18 areyieldably urged against the opposing surfaces of the resist portions 15and 16 and the intersections of the planes of the back portion 17 andthe planes of the grasping portions 18 and 18 dene axes about which therespective grasping portions are resiliently deflected. It may be notedthat the opposing edges 19" of the grasping portions are spaced fromeach other a distance greater than the diameter of the rivet 13, whenthe locking strip is assembled but has not received or joined wallpanels. Upon insertion of the wall panelsl 1 and 3 as illustrated inFigs. l and 2, these longitudinal edges 19" virtually abut the shanks ofthe rivets 13. The resiliency of all of the metal employed in thelocking strip 12 is therefore utilized in pressing the grasping portionsagainst the edge areas of panels 1 and 3. These edge areas may beinserted with relative ease under the urging of a few light blows of ahammer but can only be removed with a great deal of diiculty after theyhave once been inserted into the locking means.

At this time attention is called to a method of treating the wall panelsso as to permit relatively light-weight or small gauge sheet metal to beused without loss of strength or rigidity. For purposes of facilitatingdescription and simplifying the drawings, only panel 1 has been shown sotreated. By referringto Figs. 1 and 2, it will be noticed that panel 1is provided with two sets of elongated but interrupted indentations (andresulting bosses). The metal has been deformed to form one set ofsubstantially parallel indentations, such indentations being indicatedat 21, 22, 23 and 24, and another set of indentations extending in linesat right angles to the lines of the first set of indentations, suchsecondary -indentaparts before any panels are inserted.

tions being indicated at 25, 26, 27I and 28. Each set of indentations isinterrupted by the other set, it being noted that indentations 23 and 24are interrupted by indentation 25, and indentation 25 is spaced from allof its adjacent indentations by undeformed metal. Indentation 25 isinterrupted from indentation 26 by another indentation running at rightangles thereto, etc. It may also be noted that these indentations allstop short of the longitudinal and transverse edges of the panel 1,leaving such edges in their original planar condition so as to presentsmooth marginal edge areas adapted for insertion into suitable lockingmeans.

It has been found that the use of two sets of mutually interruptedelongated identations, each set extending in a direction substantiallytransverse to the direction of the other set, permits the use of alight-weight metal, say 20 gauge, with an apparent stiffness, rigidityand strength normally obtained by the use of 26 and 28 gauge metal.Since these indentations have a maximum depth of not over about fourtimes the actual thickness of the metal, they do not present a surfacewhich interferes with the smooth flow of air or gases thereover. Thismethod of construction saves approximately one-half the weight.

The locking means of the present invention need not take the form ofseparate locking strips and backing members as illustrated in Fig. 3 butmay be made an integral part of a sheet. This method of utilizing thepresent invention is illustrated in Fig. 4 and as there shown the sheetor panel 2 is provided with an integral locking means along eachlongitudinal edge for frictionally receiving and holding the edge areasof side panels 3 and 4. It will be noted that the longitudinal edge ofpanel 2 has been bent to form an anchor portion 34 and an upstandingresist portion 35. Held within the included angle is the locking strip32 provided with its grasping portions 38 and 38 bent toward each otherso as to present a grasping face opposing the resist 35. The lockingstrip is attached to the anchor portion of the backing element or panelby means of spaced rivets or the like 33. A similar construction is usedat the other longitudinal edge of the panel 2. It will be evident thatall of the material necessary to form a completed duct can therefore besent in the form of top and bottom panels made in accordance with Fig. 4and side panels made of simple sheets of metal having straightrectilinear undeformed edges. Shipment in its knocked down form occupiesbut little space and the entire duct can be readily assembled on the topor bottom panels without the use of special tools.

Locking means such as 40, used for connecting abutting ends of panelslying in the same plane, are illustrated in Figs. 5 and 6. Fig. 5 is atransverse section illustrating this type of locking means connectingpanels 4 and 5. It will be noted that in such locking means the backingmember 41 is substantially identical to the locking strip 42. Thebacking member includes an anchor portion 44, longitudinal edge areasbeing bent to form the resist portions 45 and 46. The locking strip 42comprises a back 47 lying in a plane substantially parallel to the planeof the anchor portion 44, longitudinal edge areas of this back 47 beingbent to form the grasping portions 48 and 48', the grasping portionspresenting grasping faces 49 directed toward the resist and adapted forfrictionally holding the edge area of a panel inserted between thegrasping portion and the opposing resist. The backing member and thelocking strip are connected together by means of small bolts 43 passingthrough the anchor portion and back of the backing member and lockingstrip, respectively.

As indicated in Fig. 6, resiliency of the formed elements is againemployed in generating a high frictional grasp upon the edge areas ofpanels. The right hand portion of Fig. 6 illustrates the arrangement ofthe formed It will be noted that the inner edge 49 of the graspingportions 46 and 48 is spaced from the stud or bolt 43. The left handportion of Fig. 6 illustrates the position of the parts after a panelhas been inserted. After such panel has been inserted the nut on thebolt 43 is tightened, bringing the grasping portions into tirmer contactwith the edge areas of the panel, the ultimate position assumed by theparts being illustrated in Fig. 5, wherein the grasping faces 49 are inface-to-face engagement with edge areas of panels 4 and 5. Although ithas been found desirable to provide the locking means 40 with adjustablebolts, this is not necessarily true in all cases since the device may beemployed with an unadjustable connecting means such as a rivet, thegrasping faces exerting yieldable pressure against their opposingresists at all times.

Fig. 7 illustrates the utilization of the locks hereinbefore describedin combination with a frame which can be employed for increasing orreducing the cross sectional size of a duct. As there shown, the frame50, of desired rectangular plan, is provided with an external wall 51and an internal wall 52, the internal wall 52 being preferably narrowerthan the external wall. The two walls are connected with a tapering wallportion 53 and an end wall 54, thereby performing a hollow frame. Thewalls 51 and `52 now act as resist elements or backing members. Lockingstrips such as the locking strip 42 is now carried by the external wall51 and a similar locking strip 42" is carried by the internal wall 52.These locking strips 42' and 42 are substantially identical to thelocking strip 42 described hereinbefore in connection with Fig. 5. Thetwo locking strips 42' and 4 are connected together and to the backingframe 50 by means of a bolt, rivet o-r the like 43. It will be evidentthat this frame may be readily connected to the end of a duct havingwall panel 55, end areas of this panel cooperating with locking strips42 and the frame then connected to an additional duct of smaller crosssectional area having wall panels 56, end areas of such panels beinggrasped by locking strips 42". The tapering or inclined end wall 53minimizes turbulence.

Ducts for various purposes and numerous types of equipment can bemanufactured by the use of one or more aspects of the above invention.All changes and modifications coming within the scope of the claims areembraced thereby.

We claim:

1. A sheet metal duct construction element comprising: a sheet of metal,each longitudinal edge portion being provided with a locking means forfrictionally receiving and holding edge areas of another sheet of metalto form the corner of a duct, each of said locking means comprising alongitudinally extending marginal edge area of the sheet bent to form aresist port-ion lying in a plane virtually transverse to said sheet andan anchor portion `separating the resist portion from the rest of thesheet,

a locking strip provided with a back portion lying in a planesubstantially parallel to the anchor portion and longitudinallyextending marginal grasping portions bent toward each other and towardthe anchor portion; and means connecting said anchor portion and backportion to hold said locking strip with one of said marginal graspingportions presenting a grasping face in resilient contact with the resistportion in position to permit insertion of the edge of said anothersheet of metal therebetween and with the plane of the back portion andthe planes of the grasping portions assuming the configuration of thelongitudinal faces of a trilateral prism and with the intersections ofthe planes of the grasping portions and the plane of the back portiondefining the axes about which the respective grasping portions areresiliently deflected.

2. A lockingy and connecting device for sheet metal ducts and the likecomprising: an elongated backing member of resilient strip metalincluding an anchor portion and a longitudinal resist portion on eachside thereof and integral therewith, said resist portions lying inplanes inclined to the plane of the anchor portion, the angle includedbetween said resist portions being slightly less than an elongatedlocking strip provided with a medial back portion lying in a planesubstantially parallel to the anchor portion of the backing member andwith longitudinally extending marginal grasping portions bent towardeach other, each of said marginal grasping portions lying in a planewhich includes an angle of less than 90 with said back portion; saidlocking strip being nested within said backing member with said backportion in spaced relation to the anchor portion and with the planes ofthe back portion and the planes of the grasping portions assuming theconfiguration of the longitudinal faces of a trilateral prismk and withthe intersection of the planes of the grasping portions and the plane ofthe back portion defining the axes about which the respective graspingportions are resiliently deflected; and means connecting the anchorportion and back portion.

References Cited in the le of this patent UNITED STATES PATENTS1,045,740 Phillips Nov. 26, 1912 1,067,189 Murphy et al. July 8, 19131,199,357 Evans Sept. 26, 1916 1,278,343 Hester Sept. 10, 1918 1,351,613Brown Aug. 31, 1920 1,425,953 Figarsky Aug. 15, 1922 1,603,627Montgomery Oct. 19, 1926 2,105,784 Hagberg Jan. 18, 1938 2,126,499Petersen Aug. 9, 1938 2,381,178 Munyon Aug. 7, 1945 2,498,753 DeitschFeb. 28, 1950 FOREIGN PATENTS 605,534 Great Britainv July 26, 1948

